Identification and analysis of four candidate symbiosis genes from ‘Chlorochromatium aggregatum’, a highly developed bacterial symbiosis

Abstract

The consortium 'Chlorochromatium aggregatum' currently represents the most highly developed interspecific association between prokaryotes. It consists of green sulfur bacteria, so-called epibionts, which surround a central, motile, chemotrophic bacterium. Four putative symbiosis genes of the epibiont were recovered by suppression subtractive hybridization and bioinformatics approaches. These genes are transcribed constitutively and do not occur in the free-living relatives of the epibiont. The haemagglutinin-like putative gene products of open reading frames (ORFs) Cag0614 and Cag0616 are unusually large and contain repetitive regions and RGD tripeptides. Cag0616 harbours two betagamma-crystalline Greek key motifs. Cag1920 codes for a putative haemolysin whereas the gene product of Cag1919 is a putative RTX-like protein. Based on detailed analyses of Cag1919, the C-terminal amino acid sequence comprises six repetitions of the motif GGXGXD predicted to form a Ca(2+)-binding beta roll. Intact 'C. aggregatum' consortia disaggregated upon the addition of EGTA or pyrophosphate, but stayed intact in the presence of various lectine-binding sugars or proteolytic enzymes. Unlike other RTX toxins, a gene product of Cag1919 could not be detected by (45)Ca(2+) autoradiography, indicating a low abundance of the corresponding protein in the cells. The RTX-type C-terminus coded by Cag1919 exhibited a significant similarity to RTX modules of various proteobacterial proteins, suggesting that this putative symbiosis gene has been acquired via horizontal gene transfer from a proteobacterium.

Genomic analysis reveals key aspects of prokaryotic symbiosis in the phototrophic consortium “Chlorochromatium aggregatum”

“…The former protein is larger than human titin (34,350 amino acids), often considered to be the largest known protein [30]. These two genes are transcribed, encode symbiosis-specific proteins, and have been hypothesized to stabilize contacts between the central bacterium and epibiont cells [15]. Smaller but related proteins, including the ones in EP_GI-3 (Cag_0738) and EP_GI-4 (Cag_1242), could play similar roles.…”

“…chlorochromatii has been sequenced, and this enabled previous biochemical, transcriptomic and proteomic studies of Chl. chlorochromatii [15,16] . The central bacterium of “Chlorochromatium aggregatum” , hereafter denoted as “ Candidatus Symbiobacter ( Ca.…”

Quantification of Propionibacterium acidipropionici P169 Bacteria in Environmental Samples by Use of Strain-Specific Primers Derived by Suppressive Subtractive Hybridization

“…For higher resolution of identification, typing methods including random amplified polymorphic DNA (RAPD) (10,16,26), pulsed-field gel electrophoresis (PFGE), repetitive sequence-based PCR (rep-PCR), and ribotyping based on phage-related sequences (4, 6) offer solutions for strain-specific primer development. Suppressive subtractive hybridization (SSH) is a technique that identifies DNA segments that are part of one bacterial genome yet absent from another one (especially closely related ones) (1,6,7,18) or a group (28). Through the use of SSH, this study was able to identify P. acidipropionici P169-specific genomic regions for development of a strain-specific qPCR assay.…”

“…The GϩC content of propionibacteria ranges from 53 to 67 mol% (3). Five of the gene fragments identified had GϩC contents lower than that, which is an indication of lateral gene transfer (14,28). The specific DNA fragment chosen for the assay with a potential role in DNA methylation had the lowest GϩC content, 49%.…”

The Type II Secretion System Is Essential for Erythrocyte Lysis and Gut Colonization by the Leech Digestive Tract Symbiont Aeromonas veronii

“…One way that bacteria can lyse erythrocytes is by secreting hemolysin into the extracellular space (20,44,49,51). The best-studied hemolysin produced by aeromonads, aerolysin, is a pore-forming protein that leads to the release of glucose and potassium from erythrocytes, which leads to colloid-osmotic lysis and the release of hemoglobin, resulting in beta-hemolysis (8,16,49).…”